I have been having this issue for the past few major updates as well; everytime this happens, the game has the "Install" button in the library of the Plarium Play launcher, and I am forced to entirely redownload and re-install the game.
My PC is brand new (so I doubt my hard drive is dying), I've never touched or moved the game files, and my internet is working fine with everything else (whether it's general browsing, streaming or other games). Redownloading Raid through the Plarium Play client averages at 0.8mbps, when my normal internet speed is 50mbps.
For a game that's heavily focused on time gates and resource refills, it's very disruptive being unable to access the game due to abysmal download speeds and installation times. Would like to know too if there is a fix or workaround for this issue, or if it is at least a currently known issue.